Earth compaction roll pad and method



Dec. 16, 1969 Q wlLLiAMSON ET AL 3,483,806

EARTH COMPACTION ROLL PAD AND METHOD Filed March 4, 1968 s Sheets-Sheet 1 6521940 77 51 5606262 BY 194/92, l7! 779K474 Dec. 16, 1969 A. o. WILLiAMSON ET L 3,433,806

EARTH COMPACTION ROLL PAD AND METHOD Filed March 4, 1968 3 Sheets-Sheet 2 I H 2.2 W 20 l FIEZ .4770 ENE);

United States Patent EARTH (ZBMPACTIUN RGLL PAD AND METHOD Archie O. Williamson, Edina, Harry H. Takata, Golden Valiey, and Gerald Gfroerer, Crystal, Minn., as-

signors to American Hoist & Derrick Company, Minneapoiis, Minn., a corporation of Delaware Filed Mar. 4, 1968, Ser. No. 710,208 Int. Cl. EOlc 19/26; E02d 3/04 US. Cl. 94-50 4 Claims ABSTRAET OF THE DISCLOSURE In the building of roads, airstrips or the like it is necessary that the underlying soil materials be pre-stressed to a point equal to or greater than the stresses to which the surface material will be eventually subjected to when in use. This is accomplished by consolidating the soil by compaction from above normally by subjecting the soil to pressures of weight carrying pneumatic tires or rollers.

Pneumatic tire rollers have achieved increasing popularity for soil compaction during recent years due to the fact that by changing tire pressure during soil consolidation the contact area of the roller with the soil can be selectively varied. Thus it is customary to use a relatively low tire pressure with broad surface contact during the initial pass or passes over loose soil so as to develop structural strength in the soil in substantial depth through large pressure bulbs. Tire pressure is then progressively increased during subsequent passes decreasing the contact area elevation of newly created pressure bulbs in the soil.

Obviously, the contact area of a steel wheel or drum with the soil cannot be selectively adjusted as in the case of a pneumatic tire. However, as material consolidates under a steel roll the arc of contact with the surface automatically becomes shorter.

One type of roller in common use for soil compaction incorporates a segmented roll for transmitting the necessary weights and pressures to the ground. This type of roll has a cylindrical framework or drum with a plurality of spaced annular rows of pads mounted thereon for engagement with the soil as the roll is pulled or driven over the ground rotating about its frame axis. As exemplary of such segmented rollers and their mode of operation at tention is directed to Patents No. 2,754,734 to A. W. Gardner; No. 3,067,658 to Palmiter; and No. 2,276,337 to H. L. Gardner.

The aforementioned patents recognize the advantages of segmented rolls in soil compaction and in their combined teachings point out the importance of developing structural strength in soil by providing pads having earth compacting surfaces which progressively decrease in area as the relative compaction of the soil increases. In other words, the roll pads are so configured as to distribute the compacting pressures over a greater area when the soil is loose and the same pressures over a lesser area when the soil has reached a high percentage of relative compaction.

Gardner Patent No. 2,754,734 discusses at length the "ice Taylor pressure bulb theory. Where a relatively large pad or bearing surface is used on loose material, the material under the pad is stressed to a greater Width and depth than where a smaller pad is used. Thus, the rolls described in the aforementioned patents desirably build up structural strength in the soil over a big area during the initial passes with the pads creating smaller and smaller pressure bulbs at progressively lesser depths.

While the aforementioned segmented rolls carry out soil consolidation in a manner similar to pneumatic tire rollers where tire pressures are progressively increased, it is believed that they can be greatly improved upon both from the standpoint of having better traction and providing more rapid compaction.

The primary object of the present invention is to provide a new and improved pad for a compaction roll which will provide the desired degree of compaction or stress fewer passes than other segmented rolls by simultaneously creating relatively deep and relatively shallow pressure bulbs in the soil which overlap each other.

Another object of the invention is to provide a method of compacting soil more quickly than those known heretofore without the use of additional weight or compactron forces.

Another object of the invention is to provide a soil compaction roll with a construction giving it improved traction in soils of varying degrees of relative compaction.

With these objects in view the invention broadly comprises providing a segmented roll with rows of compaction pads each of which has a stepped outer surf-ace with one smaller portion of the pad projecting outwardly beyond the base plate of the pad and being mounted centrally thereon with said smaller portion and base plate each having an outer surface adapted for flat pressure engagement against the ground to respectively create different sized pressure bulbs within the soil.

The above mentioned and additional objects of the invention will be brought to light during the course of the following specification, reference being made to the accompanying drawings, in which:

FIG. 1 is a partial side elevation of a compaction roll having pads constructed in accordance with one embodiment of the present invention.

FIG. 2 is a section through the roll taken on line 2-2 of FIG. 1.

FIG. 3 is an enlarged fragmentary elevation showing one of the roll pads in compacting engagement with the ground surface while the surface portions are still relatively loosely packed.

FIG. 4 is similar to FIG. 3 but showing the pad in engagement with the ground in a relatively high percentage of relative compaction.

FIG. 5 is an inverted plan view of the pad shown in FIGS. 3 and 4 from the bottom or ground engaging side thereof.

FIG. 6 is a side elevation of a modified form of the pad in the same relative ground engaging position as shown in FIG. 4.

FIG. 7 is an inverted plan view of the pad shown in FIG. 6.

FIG. 8 shows the pad of FIGS. 3 to 5 in elevation as it is positioned during the first compacting period in its engagement with relatively loose soil showing in a somewhat diagrammatical manner earth sections wherein a small pressure bulb is formed simultaneously with and within a larger one.

FIG. 9 is similar to FIG. 8 but showing the pad during its second compacting period forming second pressure bulbs in the soil respectively overlapping those formed in FIG. 8.

FIGS. 10, 11 and 12 show the pad of FIGS. 6 and 7 in elevation in three different positions as it rolls over loose soil to form one small pressure bulb betwen two partially overlapping larger ones.

Referring now more particularly to the drawings reference characters will be used to denote like parts or structural features in the different views. The compaction roll here designated generally at may form the wheels of a self propelled compactor or may be one or more cylindrical rolls or drums on a trailer drawn by a tractor or other draft vehicle. It is, of course, important that the vehicle supported by the roll or rolls 10 be sufliciently weighted to transmit the desirable compaction pressures through rolls 10 to the ground surface over which they roll.

In the particular form shown the roll 10 is carried on a pneumatic tire 11 mounted on an axle supported wheel 12. The roll comprises a drum 14 having an annular seat 15 mounted on the interior thereof for seating the inflated tire 11 and thus providing a cushioned mounting of the drum 14 on the wheel 12. On its outer periphery drum 14 carries a plurality of annular flanges 16 equally spaced axially along the drum. These flanges may be referred to as pad supports as each flange carries a plurality of pads here each designated generally by the numeral 18.

Flanges 16 have an irregular outer periphery, as best seen in FIG. 1, with a continuous series of uniform humps or undulations 19 (FIG. 3) each prescribed by a flat central crest denoted at 20 with sides 21 and 22 angling upwardly, in the undulation shown, and outwardly from each end of the crest to the next adjacent undulation. The crest curves gradually into side 21 as at 24.

Each pad 18 comprises generally an angular base plate and an outer plate 26, which will be referred to as a heel block, which are arranged in a stepped relation. Plate 25 is rectangular as shown in FIG. 5 and is bent in the longitudinally central portion to conform to the edges 29, 24 and 21 of an undulation 19. Plate 25 is approximately twice as long as it is wide and is securely welded along its longitudinal center line to the flange 16. The outer, or in FIGS. 3 and 4 bottom, surface of plate 25 denoted at 27 accordingly has the same fore and aft contour as the edges 21, 24 and 20.

Heel block 26 is shorter and narrower than plate 25 but has a similar shape being bent at its longitudinal center as shown. It is bent to a smaller angle (about 140 degrees) than plate 25 so that when mounted centrally on the surface 27 as by welding its ends at 28 and 29, the central portion thereof will be spaced away from the central portion of plate 25. The space between plates 25 and 26 may be filled in. The outer or bottom surface of the heel block 26 is denoted by the numeral 30 and in this embodiment is approxiately half as large in area as surface 27.

In operation during the initial passes of the roller over loose soil S as shown in FIG. 3, the heel block 26 will penetrate through the ground surface providing excellent traction and the base plate 25 will contact the ground surface with compaction being transmitted from the roll by the surface 27. With continued passes the soil will be consolidated with the result that eventually only block 26 will contact the soil.

A clearer understanding of the compacting etfect that pad 18 has upon the soil as it rolls thereover will be understood by reference to FIGS. 8 and 9. As the rotationally leading portion 27 of the relatively broad surface 27 comes into horizontal engagement with the ground, it will transmit the roller pressures in a downward direction throughout a substantially broad and deep area of the soil creating a large pressure bulb therein denoted diagrammatically by the circle A. At the same time the rotationally leading portion of the block 26 will penetrate the soil in the upper portion of the bulb A and, because of its smaller dimension, the surface 30 will exert downward pressure to create a smaller pressure bulb denoted by the circle B. As the pad then tilts forwardly to the position shown in FIG. 9, the front but rotationally trailing sur- 4 face portions 27 and 30 respectively on the members 25 and 26 will come into horizontal compacting engagement with the soil. Large and small pressure bulbs denoted by circles C and D are thus created.

It will be understood that pads 18 are arranged in staggered relation in the adjacent rows 0n drum 14 so that the entire ground area covered by the roll is compacted with overlapping large and small pressure bulbs.

With succeeding passes of the roll and as the percentage of relative compaction of the soil increases, a small surface area of plate 25 and ultimately of block 26 Will engage the ground, thus creating smaller and smaller pressure bulbs until the desired degree of compaction has been reached.

In the second form of the invention shown in FIGS. 6 and 7, a different form of pad denoted generally at 34 is mounted on the flange 16. It comprises a base plate 35 which is identical in size and shape to plate 25 or' the preferred embodiment. However, in place of the plate 26 an oval shaped heel block or button 36 is integrally mounted on the plate 35 at the center of its outer surface 37. The bottom or outer surface of the block 36 is substantially flat and is denoted by the number 38.

The advantages and principles of operation of pad 34 are the same as those set forth for pad 18. During the initial rolling stages where relative compaction is very low there will be maximum contact of the pad with the ground soil 5 as desired through surfaces 37 and .38. Moreover the block 36 will provide the necessary traction in sand or loose soils. During succeeding passes the pad will gradually walk up with a smaller and smaller portion of surface 37 contacting the soil until all of the eight is transmitted from surface 38 to the soil.

The compacting effect of pad 34 will be more clearly understood by referring to FIGS. 10 to 12. As the rotationally leading portion 37 of the relatively broad surface 37 comes into horizontal engagement with the ground it will transmit the roll pressures in a downward direction throughout a substantially broad and deep area of the soil creating a large pressure bulb therein denoted diagrammatically by the circle E. As the roll advances the block 36 will penetrate the soil with surface 38 creating a smaller and denser pressure bulb denoted at F. As the pad then tilts forwardly to the position shown in FIG. 12 the front surface portion 37 of base plate 35 will come into compacting engagement with the soil 5 creating a second large pressure bulb G in overlapping relationship with the bulbs denoted at E and F.

With repeated passes of the roll over the same area a smaller and smaller surface area of base plate 35 will engage the soil and ultimately only surface 38 of block 36 will transmit the compacting pressures.

By using these stepped pads and simultaneously creating a small pressure bulb of greater density within a larger pressure bulb of lesser density, the time period during which the material in a given area can be consolidated to the desired density is substantially reduced.

Other stepped pad configurations would undoubtedly work with effectiveness. For example, a base plate could be provided with several cylindrical blocks similar to heel block 36 of progressively smaller diameters mounted concentrically one upon the other with the smallest at the soil penetrating end. Such a pad would simultaneously create a series of pressure bulbs of varying size and density one within the other.

As hereinbefore mentioned another advantage in the stepped type of pad lies in the improved traction that it aifords. This is particularly important in sandy and loam soils.

The invention accordingly provides an improved pad structure and method for eifectively consolidating ground soil materials.

It is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims. Having now therefore fully illustrated and described our invention, what we claim to be new and desire to protect by Letters Patent is:

1. In an earth compacting roll of the segmented type having a cylindrical frame and a plurality of compaction pads mounted in spaced relation about the periphery of the frame for rolling contact with the ground surface as the frame is moved thereover about its axis, each said pad comprising a base plate with a heel block mounted thereon respectively presenting inner and outer compacting surfaces spaced radially of the frame, the heel block being smaller than the base plate and spaced inwardly of the peripheral edges of the base plate so that said surfaces simultaneously exert downward compacting pressure upon an earth section to create two different sized pressure bulbs therein at least partially one within the other.

2. The subject matter of claim 1 wherein said base plate compacting surface has front and rear flat portions arranged at a broad angle to successively engage the earth broadwise and each create a pressure bulb therein.

3. In a pad on a segmented roll carrying a plurality of rows of such pads and adapted to be rolled along a ground surface to compact the soil thereunder, said pad having an elongated base plate extending along the periphery of the roll in a direction generally around the rolling axis and adapted for relatively broad contact with the ground surface as the roll is moved, said base plate having a flat exterior surface adapted to come into horizontal contact with the ground surface to transmit pressures from the roll vertically to the soil to create a pressure bulb in the soil, and a heel block mounted on the base plate to project beyond said exterior surface and extend into said pressure bulb, said heel block having a flat surface substantially smaller than said base plate surface and adapted to come into horizontal engagement with the soil to transmit pressures from the roll and create a second pressure bulb in the soil of greater density than the first mentioned pressure bulb and at least in partially overlapping relation thereto.

4. In an earth compacting roll of the segmented type having a cylindrical frame and a plurality of compaction pads mounted in spaced relation about the periphery of the frame for rolling contact with the ground surface as the frame is moved thereover about its axis, each said pad having a stepped exterior configuration presenting independent inner and outer compacting surfaces spaced radially of the frame adapted to simultaneously exert downward compacting pressure upon an earth section to create two different sized pressure bulbs therein at least partially one Within the other, said pad comprising a base plate presenting an inner compacting surface having front and rear fiat portions arranged at a broad angle to successively engage the earth and each create a pressure bulb therein, and a disk block mounted centrally on the inner compacting surface to project from the intersection between the front and rear surface portions to present an outer compacting surface which is substantially normal to the radius of the frame.

References Cited UNITED STATES PATENTS 2,035,627 3/1936 West 94-46 2,754,734 7/1956 Gardner 94-50 3,040,638 6/1962 Atkinson 94--50 3,276,337 10/1966 Gardner 945O JACOB L. NACKENOFF, Primary Examiner US. 01. X.R. 301-43 

